Medical Physics is engaged in the development of noninvasive methods of extracting hemodynamic data, normally only accessible by use of highly invasive right heart catheterizations. The methods employ inert gases, in tracer concentrations, applied at the airway and measured at the nose by a gas analyzer specifically developed for this purpose. Recently, we have discovered that by adding stable (non-radioactive) tracers of oxygen and carbon dioxide to the tracer mix, arterial blood gas and pH measurements can also be obtained noninvasively -which if sufficiently accurate - could eliminate the need for arterial sticks (which have associated long lasting pain), commonly used to obtain arterial blood samples for blood gas and pH analysis by the blood gas laboratory. Additionally, the new method could routinely provide measurements of mixed venous oxygen content, a parameter which currently requires access to blood by a right heart catheter. Therefore, by eliminating the need for arterial sticks and/or central venous catheterizations, blood gas and pH measurements, would be available to a wider range of patients. These include patients in clinics and small rural hospitals which may not have well equipped blood gas laboratories or well trained personnel to operate them on a twenty-four hour basis. Therefore, a goal of this project is to demonstrate that noninvasive pH and blood gas measurements can be made with sufficient accuracy to meet clinical standards. A second goal is to demonstrate that hardware requirements of the monitor can meet the economic constraints of the blood gas industry.